Re: [PATCH] Fix vc_screenbuf leak via con_init()

[Johannes Weiner]

Hi Pekka,

On Mon, Jul 13, 2009 at 05:04:58PM +0300, Pekka Enberg wrote:
> On Mon, 2009-07-13 at 14:12 +0100, Catalin Marinas wrote:
> > Commit a5f4f52e replaced the alloc_bootmem() with kzalloc() but didn't
> > set vc_kmalloced to 1 and the memory block is later leaked. The
> > corresponding kmemleak trace:
> > 
> > unreferenced object 0xdf828000 (size 8192):
> >   comm "swapper", pid 0, jiffies 4294937296
> >   backtrace:
> >     [<c006d473>] __save_stack_trace+0x17/0x1c
> >     [<c000d869>] log_early+0x55/0x84
> >     [<c01cfa4b>] kmemleak_alloc+0x33/0x3c
> >     [<c006c013>] __kmalloc+0xd7/0xe4
> >     [<c00108c7>] con_init+0xbf/0x1b8
> >     [<c0010149>] console_init+0x11/0x20
> >     [<c0008797>] start_kernel+0x137/0x1e4
> > 
> > Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> > Cc: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
> 
> Reviewed-by: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
> 
> > ---
> > 
> > (note that detecting this requires additional kmemleak patches for early
> > log stack traces which are planned for the next merging window)
> > 
> >  drivers/char/vt.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/drivers/char/vt.c b/drivers/char/vt.c
> > index 7947bd1..f6ac4c2 100644
> > --- a/drivers/char/vt.c
> > +++ b/drivers/char/vt.c
> > @@ -2881,7 +2881,7 @@ static int __init con_init(void)
> >  		INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK);
> >  		visual_init(vc, currcons, 1);
> >  		vc->vc_screenbuf = kzalloc(vc->vc_screenbuf_size, GFP_NOWAIT);
> > -		vc->vc_kmalloced = 0;
> > +		vc->vc_kmalloced = 1;
> >  		vc_init(vc, vc->vc_rows, vc->vc_cols,
> >  			currcons || !vc->vc_sw->con_save_screen);
> >  	}
> > 
> 
> We can probably get rid of ->vc_kmalloced completely now that the
> bootmem allocator is no longer used by the driver.

That's what I thought, too.  Copied Alan.  Patch as follows:

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